Venular, but not arterial, endothelium sequesters MIP-2, and the chemokine is concentrated in junctional regions. Confocal microscopy images of cremasteric vessels (stained with anti-CD31 mAb). (A) FITC-conjugated MIP-2 (green) administered extravascularly in a gel is sequestered in and around venules (red, continuous arrow) but not in arterioles (red, dashed arrow). (B) MIP-2 administered intra-arterially is not sequestered in arterioles (green), but in (C) venules (green), as visualized by injection of fluorescently labeled anti–MIP-2 mAb (red). (D) Representative in vivo spinning disk confocal images of intravascular sequestration of FITC-labeled MIP-2 (green, administered in a gel) concentrated to endothelial cell junctions (red). Neutrophils were stained with anti–Gr-1 mAb (blue).